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arXiv · 2510.26858

Regularization of Gauss-Bonnet Gravity in Riemann-Cartan Geometry

Jianhui Qiu·Ling-Wei Luo·Chunhui Liu·Chao-Qiang Geng
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Abstract

We extend the conformal dimensional-derivative regularization of four-dimensional Gauss- Bonnet gravity to Riemann-Cartan geometry, obtaining a regularized action whose torsionless limit equals the well-known regularized four-dimensional Einstein-Gauss-Bonnet model. Varying independently with respect to the scalar, tetrad, and spin connection yields field equations that remain strictly second order in covariant derivatives, thereby avoiding Ostrogradsky-type instabil- ities. Within this framework we obtain static, spherically symmetric black holes carrying torsion hair, showing that the regularized Gauss-Bonnet interaction can support long-range torsion hair without invoking extra dimensions.

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Jianhui Qiu, Ling-Wei Luo, Chunhui Liu, Chao-Qiang Geng. 2025-10-30. Regularization of Gauss-Bonnet Gravity in Riemann-Cartan Geometry. https://arxiv.org/abs/2510.26858

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